Welcome. I think the most important thing is a case. I use an Otterbox Commuter Case.
Other than that, app wise - depends on what you use your phone for.
I use Camera+ and PicCollage for pictures
Dropbox, Turbo Scan, office mobile and Usb Sharp Pro for work
Flipboard for news
BBM and Facebook messenger for messaging
Podcasts
My fitness pal for calorie counting
Evernote
Blueletterbible
Bible
Onedrive
You may need to do some of the following to help with battery life
26 ways to improve your iPhone's battery life | ZDNet
I hope this helps!